Paving stone set and process and device for the manufacture thereof

ABSTRACT

Paving stone set and process and device for the manufacture thereof. 
     In the case of lawn-paving blocks formed from paving stones (10) spaced at a considerable distance apart, these are joined together, against relative displacements, by a holding grid (11) embedded in the paving stones (10) and comprising tension-resistant strands. The said holding grid allows the transfer of traction forces and hence the reciprocal safeguarding of the paving stones (10) within a paving stone set held together by the holding grid (11). 
     The manufacture of the paving stone sets is effected in a concrete stone mold which is conventional in its principle. A flask (19) disposed on a molding plate (28) and a drawing sheet (29) is divided in the horizontal plane (33), creating a top part-flask (34) and a bottom part-flask (35). The holding grid (11) is clamped between the two part-flasks during pouring of the concrete. Following the completion of a paving stone set, the bottom part-flask (35) is withdrawn from the concrete stone mold. Demolding can now be carried out in the usual manner.

The invention relates to a paving stone set for lawn paving, in whichthe paving stone set comprises concrete paving stones which are spacedapart, creating wide longitudinal gaps and transverse gaps suitable forplant growth, and are joined together by holding grids and securedagainst displacement. The invention further relates to a process and adevice for the manufacture of paving stone sets.

Paving blocks, which allow plant growth within gaps between the pavingstones, are gaining increasingly in importance. In order to ensure aload-bearing capacity of the so-called "lawn paving blocks" in respectof stationary and--to a limited extent--rolling traffic, the pavingstones need to be secured against displacement. For this purpose,spacers have hitherto been disposed in the gaps, by means of whichspacers the adjacent paving stones are mutually supported. In the caseof the lawn paving according to EP-A-259 735, the paving stones aremutually supported by spacers which, after a certain time, perish in theground.

The laying of paving blocks of this type is complex. Moreover, thespacers have to be produced and kept handy as separate elements of thepaving block.

From EP-A-0 004 364, a laying unit made from concrete paving stones isknown, in which the paving stones are joined by means of a network andby means of concrete webs. The concrete webs extend in the region oflongitudinal gaps and transverse gaps. The network is disposed closelyadjacent to the bottom side of the concrete paving stones. The holdinggrid, both in the region of the concrete paving stones and in the regionof the concrete webs and longitudinal and transverse gaps, is embeddedin concrete.

U.S. Pat. No. 1,592,591shows a device for the manufacture of clay bricksand solid bricks joined together by a wire grid. The interconnectedbricks serve as an outer lining for walls. The bricks are spaced apart,so that transverse and longitudinal gaps are formed. These are thenfilled in with mortar. The production mold comprises a top part and abottom part. The bottom part is closed off on its bottom side by a base.Parallel to this base runs a partition plane which divides the mold.

NL-A-6 803 753 shows an individual concrete stone, which is passedthrough by a grid, a process and a device for the manufacture of saidconcrete stone.

The object of the invention is to propose, for the design of a lawnpaving block and its production, measures which represent asimplification compared to the previous solutions and which ensuremoreover, in a simple manner, the long-term securement of the pavingstones of the installed paving block.

In order to achieve this object, the paving stone set according to theinvention is characterized in that the concrete paving stones are joinedtogether exclusively by the holding grid, in that the holding gridconsists of tension-resistant and non-perishable elastic material andlies continuously exposed in the region of the longitudinal gaps andtransverse gaps, and in that the holding grid, exclusively in the regionof the concrete paving stones, is fully embedded in the latter, and inthat the holding grid, at a distance from a bottom side of the concretepaving stones, is embedded in the latter, which distance corresponds toone-quarter to one-third the total height of a concrete paving stone.

A paving stone set respectively comprises a group of simultaneouslyproduced paving stones, which, in their manufacture, are joined togetherinto a unit by a holding grid embedded in the concrete. The holding gridcomprises longitudinal strands and transverse strands, which are capableof absorbing tensile loads. The paving stones of the lawn paving areconsequently secured, in terms of their relative position to oneanother, by members which are capable of bearing a tensile load. In theregion of the longitudinal gaps and transverse gaps, no furtherconnecting or supporting members for the paving stones are arranged.

The holding grid is configured such that plant growth in the otherwisecontinuously exposed longitudinal gaps and transverse gaps is notimpaired. The distances between the longitudinal strands and transversestrands are also chosen according to the invention such that, in theproduction of the paving stones, the fresh concrete is able to passthrough openings or meshes in the holding grid. The spacing between thestrands measures, for this purpose, 2 cm to 5 cm, preferably around 3cm.

The holding grid preferably extends at a distance from a side of thepaving stones, which bottom distance corresponds to approximatelyone-third of the height of said paving stones.

As a result of this arrangement of the holding grid, special measuresare necessary in the production of the paving stone sets. Manufacture isintended to be effected industrially in a conventional stone-moldingmachine. This is equipped with a concrete mold, which is known inprinciple. Forming part of this is a molding plate, on which theconcrete stones are molded and remain until fully hardened. Also formingpart of the concrete mold is a frame-like flask having die cavitieswhich are open at top and bottom and are limited by longitudinal wallsand transverse walls. Finally, pressure rams are provided, which enterinto the die cavities from above in order to compact the concrete. Inaddition, the concrete mold usually contains a drawing sheet disposedbetween the flask and the molding plate.

A thus configured concrete mold is equipped with a flask which isdivided in height, namely in a plane running at a distance from the base(molding plate), and consequently comprises a top part-flask and abottom part-flask. The two part-flasks together form, in each case, thedie cavities. The holding grid is disposed between the part-flasks andis clamped or fixed between them.

According to the invention, the bottom part-frame is speciallyconfigured, namely in such a way that, following the production of theconcrete stones of a paving stone set, the bottom part-flask can bewithdrawn, in a certain direction, from the region of the concrete mold.The bottom part-flask therefore exhibits transverse walls runningexclusively in the transverse direction or in the direction of thedrawing motion.

Further features of the invention relate to the manufacture of thepaving stone set and to the configuration of the concrete mold. Detailsof the latter and of the paving stone set are explained in greaterdetail below with reference to the drawings, in which:

FIG. 1 shows a paving stone set or a part thereof in plan view,

FIG. 2 shows a section through the paving stone set according to FIG. 1in the sectional plane II--II,

FIG. 3 shows a section through the paving stone set according to FIG. 1in the sectional plane III--III,

FIG. 4 shows a concrete mold for the manufacture of paving stone setsaccording to FIG. 1 in top view.

FIG. 5 shows the concrete mold according to FIG. 4 in cross-section, inpart having the pressure ram raised,

FIG. 6 shows the concrete mold in longitudinal section, in arepresentation corresponding to FIG. 5,

FIG. 7 shows a detail of the concrete mold in longitudinal section, thescale having been heavily enlarged,

FIG. 8 shows the individual parts of the concrete mold in a position inpreparation for a production cycle, in side view.

The illustrative embodiments represented in the drawings relate, on theone hand, to a paving stone set as a laying unit for lawn paving. On theother hand, details of a device (concrete mold) for the production ofsuch types of paving stone inserts are shown. The concrete mold can alsobe considered, however, for the production of paving stone sets whichare not necessarily used as part of a lawn paving.

The paving stone set according to FIGS. 1 to 3 comprises (concrete)paving stones 10 arranged in longitudinal and transverse rows, having asquare ground plan. The height of the paving stones 10 corresponds tothe usual height of such paving stones corresponding to the expectedload.

The paving stones 10 forming part of a laying unit or paving stone setare joined together by elastic members which are capable of bearing atensile load, namely by a continuous holding grid 11. This compriseslongitudinal strands 12 and transverse strands 13. The longitudinalstrands 12 and transverse strands 13 are joined together in the regionof nodes 14. The thus configured holding grid 11 consists of a suitablesynthetic material, e.g. polyester. Molding grids 11 of this type can becontinuously manufactured in corresponding continuous-casting machines.The material is weather-resistant and durable against tensile loads.

The holding grid 11 is embedded fully in the concrete of the pavingstones 10, namely at an adequate distance from a bottom side 15 of thepaving stones 10. In the illustrative embodiment shown, the holding grid11 is at a distance from the bottom side 15, which distance correspondsto approximately one-third of the height of the paving stone 10.

For the use of a thus configured paving stone set (FIG. 1) for lawnpaving blocks, the paving stones 10 are large distances apart, whichdistances are fixed by the holding grid 11. Wide longitudinal gaps 16and equally wide transverse gaps 17 are thereby produced between thepaving stones 10, which are arranged in rows. The longitudinal gaps 16and transverse gaps 17 have a width of 4 cm to 5 cm. Within theselongitudinal gaps 16 and transverse gaps 17, the holding grid 11 liescompletely exposed. No spacers or connecting webs are provided. Due tothe spacings between the longitudinal strands 12 and between thetransverse strands 13, openings 18 or meshes of the holding grid 11 areproduced which guarantee unhindered plant growth in the region of thelongitudinal gaps 16 and transverse gaps 17. The spacing between thelongitudinal strands 12 and between the transverse strands 13 heremeasures around 3 cm.

The laying units or paving stone sets configured in the described mannerare produced in a conventional stone-molding machine by means ofconcrete molds exhibiting certain modifications compared to theconventional concrete molds.

A concrete mold usually comprises a flask 19. This comprises an outerframe 20 having longitudinal spars 21, 22 and transverse spars 23, 24.Running within this frame 20 are longitudinal walls 25 and transversewalls 26. These bound die cavities 27, in which the paving stones 10 aremolded.

The frame 20, which is open at top and bottom, stands on a base, amolding plate 28. This can directly form the bottom extremity of theconcrete mold. The finished paving stones rest on the molding plate 28until fully set.

In the present illustrative embodiment, a drawing sheet 29 is providedas the bottom extremity of the flask 19. The drawing sheet 29 isconsequently located between the flask 19 and molding plate 28. In thedemolding operation, the drawing sheet 29 is withdrawn from the concretemold, according to arrow 30, in the horizontal direction, so that thepaving stones 10 then lie directly on the molding plate 28 and can betransported away with this once the flask 19 has been removed.

Pressure rams 31 having die plates 32 corresponding to the shape andsize of the die cavities 27 enter into these from above.

In order to embed the holding grid 11 in the paving stones 10 duringtheir manufacture, the flask 19, in the illustrative embodiment shown,is divided along an (imaginary) horizontal partition plane 33. A toppart-flask 34 and a bottom part-flask 35 are thereby produced. Bothtogether produce the whole flask 19.

In the region of the partition plane 33 there extends the holding grid11. This is brought into position prior to the filling of the concrete.The fresh concrete, which have been filled into the open die cavities 27from above, passes through the openings 18 or meshes in the holding grid11, so that the flask 19 or each die cavity 27 is filled to the top withconcrete.

The holding grid 11 is clamped or fixed between the part-flasks 34 and35. In the present illustrative embodiment, the holding grid 11 isclamped on three sides only between the part-flasks 34, 35, namely inthe region of the longitudinal spar 22 and transverse spars 23, 24.

The bottom part-flask 35 is configured such that the paving stones 10can be demolded essentially according to the conventional principle. Forthis purpose, after the paving stones 10 in the individual die cavities27 have been formed-out, the bottom part-flask 35 is initially removed.This is withdrawn from the region of the concrete mold, in thehorizontal direction, according to arrow 30. In order to enable this,the bottom part-flask 35 comprises the bottom part of the longitudinalspar 22 of the (divided) frame 20, which bottom part is situated to thefore in the direction of draw according to arrow 30. The said frame isadjoined by transverse walls 26 running in the direction of the drawingmotion or by bottom parts of these transverse walls 26. The bottompart-flask 35 consequently has no longitudinal walls 25. In this region,below the longitudinal walls 25 of the top part-flask 34, there areformed corresponding, elongated, strip-shaped cavities 41. These areinfiltrated, in the manufacture of the paving stones 10, by someconcrete, so that the finished paving stones 10 of a paving stone setexhibit, in the region of the longitudinal gaps 16, fins 36 adjacent tothe bottom side 15. These fins 36 can be eliminated by a finishingoperation. Since they only in substantially reduce the cross-section ofthe longitudinal gaps 16, they can also however remain on the pavingstones 10.

Following the withdrawal of the bottom part-flask 35, demolding canproceed in the usual manner. The pressure rams 31 remain in the pressuresetting according to FIG. 7. The top part-flask 34 is moved upwards intoa position according to FIG. 8. The pressure rams 31 are then raised.The molding plate 28, with the paving stones 10 and the holding grid 11embedded therein, can now be transported away.

In the present illustrative embodiment, the bottom part-flask 35 isconnected to the drawing sheet 29. The bottom parts of the transversewalls 26 are disposed as elongated edgings on the drawing sheet 29. Tothe said drawing sheet, there are fitted, on the one side, thrust rods37, which enable, by means of a suitable actuating member(pressure-medium cylinder), a to-and-fro motion of the drawing sheet 29.By use of the drawing sheet 29, the bottom part-flask 35 is withdrawnfrom or introduced into the region of the concrete mold.

In the present case, the holding grid 11, which corresponds essentiallyto the size of a paving stone set, is drawn section by section from aroll (not shown). After a corresponding section of the holding grid 11has been introduced into the concrete mold, the necessary piece is cutoff. In the present illustrative embodiment, there is fitted to the toppart-flask 34, namely to the longitudinal spar 22 situated to the forein the direction of draw, a cutting edge 38, which realizes theseparating cut as the part-flask 34 is lowered. The cutting edge 38 canalso be disposed outside the region of the flask 19, at a distancetherefrom, the holding grid 11 being cut off as it juts over thelongitudinal spar 22 of the bottom part-flask 35. To the cutting edge38, there is herein assigned a lower, fixed counter-blade, so that whenthe flask 19 is closed, the holding grid 11 is cut through and thelongitudinal spars 22 of the top part-flask 34 and bottom part-flask 35lie directly adjacent to each other and are thus able to clamp theholding grid 11.

In addition, the holding grid 11 is brought by the bottom part-flask 35or by the drawing sheet 29 into the position within the flask 19. Forthis purpose, the front margin of the holding grid 11, which is in eachcase exposed, is fixed to a free margin of the drawing sheet 29 or ofthe bottom part-flask 35, e.g. to hook-shaped holding members 39.

From the original setting (not shown) of the drawing sheet 29 outsidethe concrete mold, the holding grid 11, as it is unwound from the roll,is transported into the concrete mold (FIG. 8). After this, the toppart-flask 34 is lowered. The concrete is then filled into the diecavities 27, which are open at the top. The pressure rams 31 arethereafter lowered. The concrete is then compacted by a jarring table 40on which the concrete mold rests.

Following the molding of the paving stones 10, the drawing sheet 29 isfirst retracted, in the described manner, with the bottom part-flask 35,then the top part-flask 34 moved upwards and the pressure ramsubsequently raised.

The top part-flask 34 is configured such that the transverse walls 26 donot rest on the corresponding transverse walls 26 of the bottompart-flask 35. Rather, the top part-flask 34 is supported by thelongitudinal spar 21, situated to the rear in the direction of draw,directly on the molding plate 28 or on the drawing sheet 29.Furthermore, the transverse spars 23, 24 of the top part-flask 34 reston the corresponding transverse spars 23, 24 of the bottom part-flask35. The longitudinal spar 22 of the top part-flask 34, whichlongitudinal spar is situated to the fore in the direction of draw, alsorests on the longitudinal spar 22 of the bottom part-flask 35.

The paving stone sets which are thus manufactured can be mechanicallylaid in an advantageous manner. For this purpose, a laying machineaccording to German Offenlegungsschrift 34 11 350 exhibits a head forgripping a respective paving stone set. The head comprises two clampingjaws running in the transverse direction, which press the paving stones10 together during the laying operation. In order to secure the gapspacings between the paving stones 10 in the longitudinal direction, itis necessary for the head to be provided with spacers, which engage inthe longitudinal gaps 16 and fix the paving stones 10, during laying, atcorresponding distances apart.

The described concrete mold is also suitable for the manufacture ofpaving stone sets or laying units which are not intended for lawn pavingblocks, but which nevertheless exhibit a fully embedded holding grid.The gaps are in this case smaller or narrower.

I claim:
 1. A device for the manufacture of paving stone sets comprisingconcrete paving stones which are spaced apart and are joined together bya holding grid,said device comprising a concrete mold having a flaskdefining die cavities for respective concrete paving stones, which flaskrests on a molding plate, whereina) the flask is divided along ahorizontal partition plane extending at a distance from a lower limit ofthe die cavities and running approximately parallel to the moldingplate, b) the flask comprises a top part-flask, fixed against horizontalmovement, and a bottom part-flask which is horizontally movable relativeto said top part-flask, c) the bottom part-flask comprises onlytransverse mold walls extending in the direction of a drawing motion ofthe bottom part-flask, and d) means for drawing off the bottompart-flask from the molding plate, relative to the fixed top part-flask,in the horizontal direction.
 2. The device as claimed in claim 1,wherein the bottom part-flask comprises a drawing sheet having said moldwalls and extending in the horizontal direction, and is movable by saiddrawing sheet horizontally out of and into the concrete mold.
 3. Thedevice as claimed in claim 1 or 2, wherein the flask is configured suchthat the holding grid can be clamped between the bottom part-flask andthe top part-flask, parts of the holding grid being respectively clampedbetween adjacent ones of said mold walls of the part-flasks.
 4. Thedevice as claimed in claim 3, wherein the holding grid can be clamped onthree sides thereof between the bottom part-flask and the toppart-flask.
 5. The device according to claim 4, wherein the toppart-flask exhibits, on the side situated to the rear in the directionof drawing a longitudinal spar, the height of which corresponds to thatof the flask.
 6. The device according to claim 5, wherein the holdinggrid, which consists of an elastic synthetic material, can be drawn froma roll by the drawing sheet which is movable to and fro, the drawingsheet exhibiting projection-like holding members.
 7. The deviceaccording to claim 1, further comprising a plurality of rams (31), onefor each cavity, which define an upper limit of the cavities.
 8. Thedevice according to claim 7, wherein said partition plane (33) extendsat a distance at approximately 1/4 to 1/3 of the total height of thepaving blocks from said lower limit of the die cavities.
 9. A processfor the manufacture of paving stone sets which comprise spaced apartconcrete paving stones and are joined together by a holding grid made upof longitudinal strands and transverse strands, whereina) a bottompart-flask is disposed on a base, b) the holding grid is then disposedon the bottom part-flask, c) after this, a top part-flask is disposed onthe bottom part-flask or on the holding grid, the holding grid beingclamped between the top part-flask and the bottom part-flask, d) theconcrete is then filled into the flask, which is open at the top, theholding grid being configured such that the fresh concrete filled intoconcrete mold is able to pass through openings formed by thelongitudinal strands and transverse strands, e) pressure rams are nextlowered into the flask from above, whereupon the concrete is compacted,f) the bottom part-flask is then withdrawn horizontally relative to thehorizontally fixed top part-flask, g) the top part-flask is next movedupwards, and h) the pressure rams are then raised.